1. Field of the Invention
The present invention relates to a lens device having a zoom lens, an imaging device equipped with this lens device and adapted to perform electronic zooming, an imaging system, a lens control system and a computer readable storage medium.
2. Description of the Related Art
FIG. 4 is a block diagram showing the configuration of a conventional lens-interchangeable video camera. In this figure, reference numeral 100 designates an interchangeable lens unit; and 200 a camera body unit to which the interchangeable lens unit is detachably attached. In the interchangeable lens unit 100, reference numeral 101 denotes a fixed front lens group; 102 a variator or zoom lens group for zooming or changing a magnification; 103 a fixed lens group; 104 a compensator or focusing lens group for performing both functions of compensating and focusing. These lens groups 101 to 104 constitute a lens system of inner focusing type.
Reference numeral 106 designates a stepping motor for moving the variator lens group 102; 108 a rotation shaft that is connected to a gear 107 through the stepping motor 106 and has a screw; 109 a rack that is movably mounted on the rotation shaft 108 and provided with the variator lens group 102. Reference numeral 105 denotes a driver for driving the stepping motor 106; and 110 a zoom encoder for detecting the position of the variator lens group 102.
Reference numeral 112 designates a stepping motor for moving the compensator lens group 104; 113 a rotation shaft that is directly connected to a stepping motor 112 and has a screw; 114 a rack that is movably mounted on the rotation shaft 113 and provided with the compensator lens group 104. Reference numeral 111 denotes a driver for driving the stepping motor 112. Reference numeral 115 designates a microcomputer (hereunder sometimes referred to as a lens microcomputer) that communicates with a microcomputer 208 of the camera body unit 200 and controls each of the drivers 105 and 111 and receives position detection information from the zoom encoder 110
Further, in the camera body unit 200, reference numeral 201 denotes an imager such as CCD; 202 CDS/AGC circuit for performing a correlated double sampling operation and an automatic gain control operation; 203 A/D converter; 204 a signal processing circuit; 205 an enlargement processing circuit for performing electronic zooming; 206 a signal processing circuit; 207 D/A converter; 208 a microcomputer (hereunder sometimes referred to as a camera microcomputer) for controlling the entire video camera and for communicating with the lens microcomputer 115; 210 and 211 zoom switches for moving the variator lens group in a tele or telephoto direction and a wide or wide-angle direction, respectively; 212 and 213 focus switches for moving a focus position to an infinite focus position and to a shortest focus position, respectively; and 209 a group of these switches.
Next, an operation of this video camera will be described hereinbelow. When the interchangeable lens unit 100 is attached to the camera body unit 200, electric power is supplied from the camera body unit 200 to the interchangeable lens unit 100. Then, an image is formed on the imager 201 from light that comes from an object through the lens groups 101 to 104. Video signals obtained by photoelectric conversion performed in the imager 201 are processed by the CDS/AGC circuit 202. Subsequently, the video signals are converted by the A/D converter 203 into digital video signals which are then sent to the signal processing circuit 204. After the signal processing circuit 204 gamma-corrects the digital video signals, the enlargement processing circuit 205 performs enlargement processing (to be described later) on the gamma-corrected video signals. Further, the signal processing circuit 206 performs balanced modulation on color signals. The processed signals are converted by the D/A converter 207 into digital analog video signals which are then sent to VTR (not shown).
Next, operations of the lens microcomputer 115 and zooming and focusing operations will be described hereinbelow. When the zooming or focusing operation is designated, the lens microcomputer 115 determines the rotation speed and direction of each of the motors 106 and 112 by executing programs. Further, the lens microcomputer 115 outputs control signals representing the determined rotation speed and direction, and controls the stepping motors 106 and 112 through the drivers 105 and 111, respectively. Incidentally, regarding the zooming operation, the lens microcomputer 115 determines the rotation direction of the motor 106 according to the states of the switches 210 and 211, which are represented by signals outputted from the camera microcomputer 208, respectively. Regarding the focusing operation, in the case of adjusting focus by a manual operation, the rotation direction of the motor 112 is determined according to the states of the switches 212 and 213, which are represented by signals sent from the camera microcomputer 208. On the other hand, in the case of adjusting focus by an autofocusing (AF) operation, the rotation direction of the motor 112 is determined by executing AF processing routine in the lens microcomputer 115.
Each of the motors 106 and 112 rotate by being controlled according to the aforementioned control signals. Thus, the rotation shaft 108 rotates through the gear 107. Moreover, the rotation shaft 113 rotates. Each of the racks 109 and 114 moves back and forth together with a corresponding one of the lens groups 102 and 104. Consequently, predetermined zoomed and focused conditions of the video camera are obtained.
Next, enlargement processing (namely, electronic zooming) to be performed on an image in the enlargement processing circuit 205 by utilizing linear interpolation will be described hereinbelow. Enlargement processing is performed by operating the zoom switches 210 and 211 by a cameraman. When an original image shown in the left side part of FIG. 5A is expanded into an enlarged image shown in the right-side part thereof, scan lines representing the original image are as illustrated in the left-side part of FIG. 5B, and scan lines representing the enlarged image are as illustrated in the right-side part thereof. In this case, the scan lines, which represent the enlarged image and are respectively indicated by dashed lines in the right-side part of FIG. 5B, are newly formed from the scan lines A to F representing the original image shown in the-left-side part thereof. Thus, each of the scan lines respectively indicated by dashed lines is obtained by multiplying data representing corresponding ones of scan lines, which are respectively indicated by solid lines in the right-side part of FIG. 5B, by weight factors (or correction coefficients) corresponding to the distances thereof and adding up resultant data. The original image can be enlarged at an arbitrary enlargement magnification by performing such linear interpolation processing in the vertical and horizontal directions.
FIG. 6 shows the configuration of the enlargement processing circuit 205. For simplicity of description, this figure illustrates only the vertical enlargement processing. As shown in FIG. 6, input video signals 300 are stored in a memory circuit 301 under the control of a memory control signal generating circuit 302. Microcomputer interface circuit 304 receives an enlargement magnification and enlargement information from the camera microcomputer 208. Based on this, an enlarged magnification determining circuit 303 outputs the enlargement magnification to the memory control signal generating circuit 302 and an interpolation coefficient generating circuit 308. The memory control signal generating circuit 302 reads signals, which respectively represent an nth line and an (n−1)th line delayed by 1 H (namely, one horizontal scanning interval) from the nth line, from the memory circuit 301. The interpolation coefficient generating circuit 308 generates interpolation coefficients corresponding to the enlargement magnification and gives the generated interpolation coefficients to multipliers 305 and 306. These multipliers multiply the signals, which respectively represent an nth line and an (n−1)th line, by the interpolation coefficients. Outputs of these multipliers are added up in an adder 307. Resultant signal is outputted therefrom as an output video signal 310.
Next, processing to be performed in the camera microcomputer 208 will be described with reference to a flowchart of FIG. 7. In step 401, the processing is started. Then, predetermined initialization is performed in step 402. Subsequently, in step 403, the camera microcomputer 208 waits for a vertical synchronization signal Vd. When the vertical synchronization signal Vd is inputted to the camera microcomputer 208, control proceeds to step 404 whereupon the camera microcomputer 208 makes predetermined communication with the lens microcomputer 115. Thereafter, the camera microcomputer 208 performs AF operation and an automatic exposure (AE) operation in step 405. Then, the camera microcomputer 208 performs electronic and optical zooming in step 406. Subsequently, control returns to step 403.
FIG. 8 is a flowchart illustrating the operation performed in the aforementioned step 404 in more detail. As illustrated in FIG. 8, the operation is started in step 501. Then, the camera microcomputer 208 sends a communication request signal to the lens microcomputer 115 in step 502. Subsequently, control advances to step 503 whereupon the camera microcomputer 208 checks whether a communication enabling signal comes thereto from the lens microcomputer 115. If so, control proceeds to step 505. If not, control advances to step 504 whereupon the camera microcomputer 208 waits for a communication enabling signal for a predetermined time. If no communication enabling signal comes thereto within the predetermined time, the camera microcomputer 208 gives up communicating with the lens microcomputer 115. Then, the camera microcomputer 208 finishes the communicating operation in step 506.
In the case that a communication enabling signals comes thereto within the predetermined time, bidirectional communication between the camera microcomputer 208 and the lens microcomputer 115 is performed in step 505. At that time, data sent from the camera microcomputer 208 to the lens microcomputer 115 includes information on the halt or moving direction of the zoom lens group, which is obtained as a result of the operation performed in the aforementioned step 406. Further, data sent to the camera microcomputer 208 from the lens microcomputer 115 includes information on the inhibition/permission of electronic zooming. Subsequently, the camera microcomputer 208 terminates the communicating operation in step 506. Then, in step 507, control returns to the aforementioned step 406.
Next, the step 406 will be described in detail with reference to a flowchart of FIG. 9. As shown in FIG. 9, an operation is started in step 601. Then, in step 602, the camera microcomputer 208 checks whether the camera is performing zooming. When both the zoom switches 210 and 211 are pushed, or when neither of the zoom switches 210 and 211 is pushed, control proceeds to step 607. When only one of the zoom switches 210 and 211 is pushed, control proceeds to step 603 whereupon it is checked which of the zoom switches 210 and 211 is pushed. If the “TELE” switch 210 is pushed, control advances to step 604. If the “WIDE” switch 211 is pushed, control proceeds to step 608.
In step 604, the camera microcomputer 208 checks whether electronic zooming permission information comes thereto from the lens microcomputer 115. If the camera microcomputer 208 is permitted to perform electronic zooming, control advances to step 605. If not, control proceeds to step 610. In step 605, the camera microcomputer 208 checks whether the zoom lens group 102 is placed at a tele end. If so, control advances to step 607. Otherwise, control proceeds to step 606 whereupon an electronic zooming operation is performed by increasing or decreasing the aforementioned interpolation coefficients according to which of the switches 210 and 211, and whereupon the camera microcomputer 208 controls the enlargement processing circuit 205 according to a result of the zooming operation. Upon completion of this control operation, the camera microcomputer 208 sends a zoom lens stop request signal to the lens microcomputer 115 in step 607. Further, in step 610, the camera microcomputer 208 sends the lens microcomputer 115 a request to move the zoom lens group to the tele side.
On the other hand, in step 608, the camera microcomputer 208 checks whether the camera is now performing electronic zooming. If so, control proceeds to step 606. Otherwise, control advances to step 609 whereupon the camera microcomputer 208 sends the lens microcomputer 115 a request to move the zoom lens group to a wide side. Upon completion of the operation to be performed in one of the aforementioned steps 607, 609 and 610, control returns to a main routine in step 611.
FIG. 10 is a flowchart illustrating processing concerning a zooming operation, which is a part of the entire processing to be performed by the lens microcomputer 115. As illustrated in FIG. 10, the processing is started in step 701. Then, in step 702, the lens microcomputer 115 checks whether the aforementioned zoom lens stop request signal comes thereto from the camera microcomputer 208. If so, namely, if the zoom lens group should be stopped, control proceeds to step 708. Otherwise, control advances to step 703 whereupon the lens microcomputer 115 checks according to the information sent by the camera microcomputer 208 which of the tele direction and the wide direction the moving direction of the zoom lens group is. If the moving direction of the zoom lens group is the tele direction, control proceeds to step 704. If the wide direction, control advances to step 705.
In step 704, the lens microcomputer 115 checks whether the zoom lens group is positioned at the tele end. If so, control proceeds to step 708. Otherwise, control advances to step 706. Further, in step 705, the lens microcomputer 115 checks whether the zoom lens group is positioned at the wide end. If so, control proceeds to step 708. Otherwise, control advances to step 706. The moving speed of the zoom lens group and the moving speed and direction of the focusing lens group are calculated in step 706. According to a result of this calculation, the zoom lens group and the focusing lens group are driven in step 707. Furthermore, in step 708, the zoom lens group is stopped.
Upon completion of the operation performed in step 707 or 708, the lens microcomputer 115 checks in step 709 whether the zoom lens group is placed at the tele end. If so, control proceeds to step 710. Otherwise, control advances to step 711. In step 710, the lens microcomputer 115 sends the camera microcomputer 208 an electronic zooming enabling signal. Further, in step 711, the lens microcomputer 115 sends the camera microcomputer 208 an electronic zooming inhibiting signal. Upon completion of the operation performed in step 710 or 711, control returns to the main routine in step 712.
As described above, in the case that the zoom switches 210 and 211 are provided only in the camera body unit 200, optical zooming and electronic zooming are realized under the control of the camera microcomputer 208. However, in the case that a zoom ring 116 to be used for manually performing a zooming operation is provided in the interchangeable lens unit 100 as illustrated in FIG. 3, the conventional video camera has the problem that it is difficult to achieve suitable and smooth control of optical zooming and electronic zooming.